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Re: [APD] Convert microSiemens to mg/liter CACO3?


I failed to make my point. You cannot measure CaCO3 with a conductivity 
or TDS meter. They simply are not directly related.

Please check out:


which is a pretty good discussion of the whole subject.

I don't use snake-oil preparations (e.g., magic elixers without any 
label contents, like "RO Right) to reconstitute RO. Short of 
extraordinary circumstances, it is far better to use tap water for the 
essential electrolytes you need. [Water softeners shouldn't be used, of 
course, for they do a hideous imbalance of the electrolytes you want. 
Great for laundry, none of us should drink softened water, IMHO, much 
less use it for fish.]

When I had too-soft water in Modesto, I found Seachem's "Equilibrium" 
brought my dying plants and fish back to health. Now I use it for 
increasing the TDS of pupfish water, etc.

>Date: Thu, 29 Sep 2005 07:40:26 -0500
>From: "Tom Wood" <tomwood2 at flash_net>
>Subject: Re: [APD] Convert microSiemens to mg/liter CACO3?
>To: <aquatic-plants at actwin_com>
>TW: "I know they are measuring separate parameters, but if you knew exactly 
>what was in the water, say by using RO water reconstituted with a product 
>like Kent's RO Right, would it be possible to estimate a conversion?"
>WH: "The factor of two conversion (uS to mg/l) is quite good enough for 
>most purposes with most ordinary tap water, IME, so such tests are a bit 
>overkill. Differential measurements of limited accuracy are quite OK for 
>such purposes as avoiding osmotic shock, the main purpose for most folks 
>wanting to know tds."
>I'm trying to get to the lowest GH I can in a planted tank and still keep 
>goldfish in it. 
Then measure the GH by titration with a test kit..uS and TDS don't tell 
you how much is as GH.

>I have a TDS meter that I can convert to microSiemens, so I 
>can start with either number. When you say "factor of two conversion (uS to 
>mg/l) do you mean that I multiply uS by 2 to get mg/l? 

No, the other way around. Hanna approximates uS as about 2X TDS ppm. TDS 
can vary from 0.45 to 1.0 times the uS, but the 0.5 average for tap 
water works pretty well. Most of us use ppm instead of mg/l, BTW. 
Basically they are the same in most situations.

>This doesn't seem 
>right because a uS reading of 360 would mean mg/l of 720 and I know it's 
>not anywhere near there. The titration test kit says it's 36, and I know 
>the water is mostly RO water.
>WH: "I always find what percent of my tds is as general hardness..." 
>I've asked Kent for this info, we'll see if they help out.
They won't help, based on the experience of others on this list.

>WH:"...so I also use tds/uS as a very quick and dirty way to estimate GH."
>Divide tds by uS to get GH?
No. Use titration (a liquid GH test kit) to find out what the ppm of 
CaCO3 equivalent is of your tap water, and take that GH figure as a 
percent of measured TDS. If it is stable (true for most, but not all 
areas) you can decide how much to dilute your tap water with RO to get 
the GH you are looking for. Depending on who's degrees you are using, 
there are about 17-18 ppm per degree.

For example, I find tap GH is often about 2/3 of TDS. If I dilute that 
tap water with RO and get a final TDS of 100 ppm, I will know the GH is 
about 65-70 ppm. Remember that GH is only part of TDS, and you must use 
your water report or a GH kit to find out just how much. The kit is much 
better, as the water report is often updated only every three years so 
should be treated with a bit of scepticism.

>PS: Is the body chemistry of a discus really that different from the body 
>chemistry of a goldfish regarding osmoregulation, or are the 
>recommendations for vastly different GH values for these fish more 
>applicable to the breeding conditions? 
Since I don't breed either, take my free advice FWIW. Osmoregulation is 
the same for both, and breeding conditions are quite different. I have 
seen Discus do very well in so-called "liquid rock" but believe the Ca++ 
and Mg++ of hard water likely keeps their eggs from developing properly 
and may discourage them from breeding at all.

Discus can live in water with so little dissolved electrolytes that it 
could be lethal to other fish. This is likely an adaptation to the soft 
waters of the well-depleted rainforest. Rain has rinsed away so many of 
the essential electrolytes that the Discus has had to evolve special 
mechanisms for maintaining healthy cell metabolism.

All fish Atlas authors seem to have a serious inability to understand 
chemistry, so they have propagated some wonderful myths in this area. 
Take it from one who has bred a lot of Amazonians (Dwarf chicklets, 
Tetras, Catfish and Angels) the need for ultra soft water is vastly 
overstated. I have bred Neon Tetras in 450 ppm TDS water that was 300 
ppm as CaCO3 equivalent hardness!

Plants, of course, generally despise too-soft water. Cell metabolism 
requires some of all four essential electrolytes (Ca, Mg, K, and Na) -- 
plus trace elements. Serious imbalance is usually fatal. Look at how 
lush plant growth is in the hard water of FL and how sparse in 
blackwater regions of the Amazon, for example. Folks in SF and other 
ultra-soft water areas either add "Equilibrium" or use beach gravel, 
such as "Lapis Lustre" to keep plants healthy.


Wright Huntley - Rt. 001 Box K36, Bishop CA 93514 - whuntley at verizon_net - 760 872-3995

 "One in four Katrina victims were white people; so if this was a racist conspiracy, it wasn't a very good one."  -- Ann Coulter

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